Semiconductor-sealing-purpose epoxy resin compound producing method

ABSTRACT

A method of manufacturing an epoxy resin composition for semiconductor encapsulating by use of a kneader provided with a suction hole on the downstream side of a kneading region in a conveying direction of the epoxy resin composition, and being provided with a supply orifice and a discharge orifice respectively disposed on the upstream side and the downstream side in the conveying direction of the epoxy resin composition, the method comprising kneading the epoxy resin composition, while discharging a volatile gas from the kneader through the suction hole, and simultaneously introducing outside air to the kneader through the supply orifice and the discharge orifice. Even under conditions of continuous operation of the kneader, it is possible to efficiently discharge a volatile gas, thereby significantly decreasing the quantity of a volatile components remaining in the kneaded epoxy resin composition. Therefore, when semiconductor devices are encapsulated with the epoxy resin composition, the generation of voids can be decreased.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing an epoxyresin composition for semiconductor encapsulating, an epoxy resincomposition for semiconductor encapsulating manufactured by the method,and a semiconductor device encapsulated with the epoxy resin compositionfor semiconductor encapsulating.

2. Description of the Related Art

In general, a resin composition for semiconductor encapsulating iscomprised of an epoxy resin having excellent electrical properties, heatresistance and mass productivity, a curing agent for the epoxy resin, acatalyst, a release agent, a flame retardant, an additive such as acoloring agent, and a filler which occupies 70 to 95 wt % in terms of acomposition ratio. Furthermore, its manufacturing method comprises thesteps of blending and mixing predetermined amounts of componentsconstituting the resin composition, kneading the mixture by the use of amixing mill, a uniaxial kneader, a combination of the uniaxial kneaderand the mixing mill, or a biaxial kneader, rolling the kneaded materialinto a sheet form, cooling the sheet, pulverizing the cooled sheet, andthen, if necessary, forming the pulverized material into cylindricaltablets. In the kneading step of these steps, the biaxial kneader whichis excellent in productivity has often been used as the kneader.

However, the biaxial kneader has a hermetically sealed inside structure,and hence, in a case where a gas is volatilized from the kneadedmaterial, the volatile gas is discharged out of the kneader through adischarge orifice of the kneader. When the volatile gas contacts with acooled member for the discharge orifice of the biaxial kneader, thevolatile gas comes to be cooled and liquefied, and the resultant liquidthen adheres to the member for the discharge orifice. Particularly, whenthe liquid adheres to a portion close to the discharge orifice of thekneader, there is a fear that the liquid mingles with the kneadedmaterial or drops onto sheet forming rolls for cooling the kneadedmaterial.

In such a case where the liquid mingles with the kneaded material, thereis a fear that voids (pores) are generated during the molding ofsemiconductor packages. Furthermore, when the liquid adheres to thesheet forming rolls, there is also a fear that a trouble occurs duringthe operation of the kneader.

As means for solving the above problem, there has been disclosed abiaxial kneader characterized by the shape of a vent port to efficientlydischarge a volatile gas (see Japanese Patent Application Laid-open No.7-314440). Furthermore, a method for carrying out the kneading operationwhile maintaining the pressure in the kneader at a reduced pressure of250 mmHg or lower has also been proposed (see Japanese Patent No.3009027 and Japanese Patent No. 3320354).

In these methods, it is necessary to seal a kneading section of thekneader with a kneaded material to create the conditions of the reducedpressure. This is apt to cause the movement of the kneaded materialtoward a suction port, clogging of a discharge orifice and the like,which makes continuous production difficult.

Therefore, at the production site of a conventional epoxy resincomposition for semiconductor encapsulating, prescribed maintenance suchas removal of the resin composition adhering to a part of the kneaderhas been carried out in a case where the kneader is continuouslyoperated.

In the meantime, in recent years, semiconductor packages are becomingincreasingly thinner so that a material for semiconductor encapsulatingis also decreasing in thickness in the package. The presence of thevoids makes it difficult to secure desired moisture resistancereliability and electric insulation properties. For this reason, therehas been a strong demand for a means for removing volatile components toprevent the generation of the voids.

Therefore, in order to solve such conventional problems, it is an objectof the present invention to provide a method of manufacturing an epoxyresin composition for semiconductor encapsulating, by which a volatilegas can be efficiently discharged even under a condition of continuouskneading operation.

SUMMARY OF THE INVENTION

The present invention is directed to a method of manufacturing an epoxyresin composition for semiconductor encapsulating by use of a kneader,the kneader being provided with a suction hole on the downstream side ofa kneading region in a conveying direction of the epoxy resincomposition, and being provided with a supply orifice and a dischargeorifice which are respectively disposed on the upstream side and thedownstream side in the conveying direction of the epoxy resincomposition, the method comprising the step of kneading the epoxy resincomposition while discharging a volatile gas in the kneader out of thekneader through the suction hole, and simultaneously introducing outsideair through the supply orifice and the discharge orifice into thekneader.

In the present invention, it is preferred that a quantity of the gas tobe discharged from the kneader is in the range of 3 to 60 m³/h, and thequantity of the outside air to be introduced through the supply orificeis in the range of 0.1 to 2 m³/h.

Another aspect of the present invention is directed to an epoxy resincomposition for semiconductor encapsulating manufactured by the methoddescribed above. In this case, it is preferred that the epoxy resincomposition for semiconductor encapsulating comprises an epoxy resin, acuring agent for the epoxy resin, and an inorganic filler. Further, thequantity of the inorganic filler to be mixed is preferably in the rangeof 70 to 97 wt % based on the total weight of the composition.

Still another aspect of the present invention is directed to asemiconductor device encapsulated with the epoxy resin composition forsemiconductor encapsulating described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of a biaxial kneader to be used in thepresent invention.

Description of Symbols  1: biaxial kneader (kneader). 10a: axial memberfor conveying a kneaded material. 10b: axial member for reversing akneaded material. 11: inner wall. 11a: inner wall on downstream side ofkneading region. 12: kneading section. 15: kneading region. 16: supplyorifice. 17: discharge orifice. 18: suction hole. 20: blower (suctionmeans). 21: suction pipe. 22: straight part of suction pipe. 23: holefor measuring quantity of sucked air. 30: shoot. 31: bottom end ofshoot. 40: outside air introducing pipe. 41: straight part of theoutside air introducing pipe. 42: hole for measuring air quantity at thesupply orifice. 50: member for discharge orifice. 60: sheet formingrolls. 65: kneaded material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be made with regard to the embodiments of the presentinvention. The epoxy resin composition for semiconductor encapsulatingof the present invention contains an epoxy resin and a curing agent forthe epoxy resin. Preferably, the epoxy resin composition forsemiconductor encapsulating further contains an inorganic filler interms of lowering of a coefficient of linear expansion.

First, the epoxy resin to be used in the present invention will bedescribed.

In the present invention, an epoxy resin commonly used for manufacturingan epoxy resin composition for semiconductor encapsulating can be used.Examples of such an epoxy resin include: a novolac type epoxy resin suchas a phenol novolac type epoxy resin, an ortho-cresol novolac type epoxyresin, or an epoxy resin having a triphenylmethane skeleton, which is anepoxidized product of a novolac resin obtained by condensation orcopolycondensation of phenols (e.g., phenol, cresol, xylenol, resorcin,catechol, bisphenol A, or bisphenol F) and/or naphthols (e.g.,α-naphthol, β-naphthol, or dihydroxynaphthalene) and a compound havingan aldehyde group (e.g., formaldehyde, acetaldehyde, propionaldehyde,benzaldehyde, or salicylaldehyde) under the presence of an acidcatalyst; diglycidyl ether such as bisphenol A, bisphenol F, bisphenolS, or alkyl-substituted or non-substituted bisphenol; a stilbene typeepoxy resin; a hydroquinone type epoxy resin; a glycidyl ester typeepoxy resin obtained by the reaction of a polybasic acid (e.g., phthalicacid or dimer acid) and epichlorohydrin; a glycidyl amine type epoxyresin obtained by the reaction of polyamine (e.g.,diaminodiphenylmethane or isocyanuric acid) and epichlorohydrin; anepoxidized product of a resin obtained by copolycondensation ofdicyclopentadiene and phenols; a biphenyl type epoxy resin; an epoxyresin having a naphthalene ring; an epoxidized product of anaphthol-aralkyl resin; a trimethylolpropane type epoxy resin; a terpenemodified epoxy resin; an aliphatic epoxy resin obtained by oxidation ofolefin bonds with peracid such as peracetic acid; and a sulfuratom-containing epoxy resin. These epoxy resins can be used singly or incombination of two or more.

Further, as for the curing agent for the epoxy resin, a curing agentcommonly used for manufacturing an epoxy resin composition forsemiconductor encapsulating can be used. Examples of such a curing agentinclude: a novolac type phenol resin obtained by condensation orcopolycondensation of phenols (e.g., phenol, cresol, resorcin, catechol,bisphenol A, bisphenol F, phenylphenol, or aminophenol) and/or naphthols(e.g., α-naphthol, β-naphthol, or dihydroxynaphthalene) and a compoundhaving an aldehyde group (e.g., formaldehyde, benzaldehyde, orsalicylaldehyde) under the presence of an acid catalyst; variouspolyhydric phenol compounds such as tris(hydroxyphenyl)methane ordihydroxybiphenyl; a phenol resin having a novolac structure containinga biphenyl derivative and/or a naphthalene derivative in a molecule; anaralkyl type phenol resin such as a phenol-aralkyl resin (e.g., a phenolcompound represented by the following general formula (I):

wherein R represents an alkyl group having 1 to 4 carbon atoms and n isan integer of 0 or more), a naphthol-aralkyl resin or a biphenyl-aralkylresin; a dicyclopentadiene type phenol novolac resin synthesized bycopolymerization of phenols and/or naphthols and cyclopentadiene; adicyclopentadiene type phenol resin such as a naphthol novolac resin; aterpene modified phenol resin; an acid anhydride such as maleicanhydride, phthalic anhydride, or pyromellitic anhydride; and anaromatic amine such as methaphenylenediamine, diaminodiphenylmethane, ordiaminodiphenylsulfone. These curing agents can be used singly or incombination of two or more. It is preferred that the curing agent ismixed with the epoxy resin so that the ratio of the number of epoxygroups in the epoxy resin to the number of hydroxyl groups in the curingagent lies in the range of 0.7 to 1.3.

The inorganic filler to be used in the present invention is not limitedto any specific one. Examples of such an inorganic filler include: fusedsilica powder; crystalline silica powder; powder or spherical beads ofalumina, zircon, calcium silicate, calcium carbonate, silicon carbide,aluminum nitride, boron nitride, beryllia, or zirconia; monocrystallinefibers of potassium titanate, silicon carbide, silicon nitride, oralumina; and glass fibers. These inorganic fillers can be used singly orin combination of two or more. Further, as for an inorganic fillerhaving a flame-retardant effect, aluminum hydroxide, magnesiumhydroxide, or zinc borate can be mentioned, and they can be used singlyor in combination of two or more. In this regard, it is to be noted thatthe quantity of the inorganic filler to be mixed is preferably 70 to 97wt %, more preferably 80 to 95 wt %, based on the total weight of thecomposition in terms of hygroscopic properties and lowering of acoefficient of linear expansion.

Further, as necessary, the epoxy resin composition of the presentinvention may contain a curing accelerator. Examples of the curingaccelerator include: imidazole compounds such as 2-methylimidazole,2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole,2-phenyl-4-methylimidazole, and 2-heptadecylimidazole; tertiary aminecompounds such as triethylamine, benzyldimethylamine,α-methylbenzyldimethylamine, 2-(dimethylaminomethyl)phenol,2,4,6-tris(dimethylaminomethyl)phenol, and1,8-diazabicyclo(5,4,0)undecene-7; organometallic compounds such aszirconium tetramethoxide, zirconium tetrapropoxide,tetrakis(acetylacetonato)zirconium, and tri(acetylacetonato)aluminum;and organic phosphine compounds such as triphenylphosphine,trimethylphosphine, triethylphosphine, tributylphosphine,tri(p-methylphenyl)phosphine, and tri(nonylphenyl)phosphine.

Furthermore, if necessary, the epoxy resin composition of the presentinvention may contain a flame retardant. Examples of the flame retardantinclude: brominated epoxy resins such as brominated bisphenol A typeepoxy resins and brominated phenol novolac type epoxy resins; brominatedpolycarbonate resins; brominated polystyrene resins; brominatedpolyphenyleneoxide resins; tetrabromobisphenol A; and decabromodiphenylether. Also, as for a non-halogen or non-antimony flame retardant, redphosphorus, red phosphorus coated with an inorganic compound such aszinc oxide and a thermosetting resin such as phenol resin, a phosphoruscompound (e.g., phosphoric ester), a nitrogen-containing compound (e.g.,melamine, a melamine derivative, a melamine modified phenol resin, acompound having a triazine ring, a cyanuric acid derivative or anisocyanuric acid derivative), a compound containing phosphorus andnitrogen (e.g., cyclophosphazene), or a compound containing a metallicelement (e.g., aluminum hydroxide, magnesium hydroxide, zinc oxide, zincstannate, zinc borate, iron oxide, molybdenum trioxide, zinc molybdate,or dicyclopentadienyl iron) can be mentioned, for example. These flameretardants can be used singly or in combination of two or more.

Moreover, as necessary, the epoxy resin composition of the presentinvention may contain a coupling agent such as epoxysilane, aminosilane,or mercaptosilane.

Moreover, as necessary, the epoxy resin composition of the presentinvention may contain various additives such as a releasing agent, acoloring agent, a silicone-based stress relaxation agent, and an iontrap agent.

A manufacturing method of the epoxy resin composition of the presentinvention comprises the steps of blending predetermined amounts ofcomponents as described above, and pre-mixing and pre-kneading ifnecessary, kneading the mixture by kneader, rolling the kneadedmaterial, cooling, pulverizing the cooled sheet, and then, if necessary,forming the pulverized material into tablets.

Next, a description will be made with regard to a kneader to be used inthe present invention. FIG. 1 is a schematic illustration which shows asectional side view of a biaxial kneader 1 that is one embodiment of thekneader to be used in the present invention.

In the kneader to be used in the present invention, a suction hole 18 isprovided on the downstream side of a kneading region 15 of the kneaderin a conveying direction of the kneaded material. Specifically, thesuction hole 18 is provided in an inner wall 11 a on the downstream sideof the kneading region.

As shown in FIG. 1, the suction hole 18 is preferably disposed in theend surface of the inner wall 11 a on the downstream side.

Further, as for axial members in a kneading section of the kneader, itis preferred that an axial member 10 a for conveying a kneaded materialis provided on the upstream side and an axial member 10 b for reversingthe kneaded material is provided on the downstream side of the kneadingregion 15. That is, it is preferred that the axial member 10 b, by whichthe conveying direction of the kneaded material is reversed to dischargethe kneaded material through an discharge orifice 17, is provided at aportion adjacent to the axial member 10 a for conveying the kneadedmaterial on the downstream side in the conveying direction, that is, onthe downstream side of the discharge orifice 17 of the kneader.

Furthermore, the suction hole is preferably connected to a blower 20 asa suction means.

In this regard, it is to be noted that, in the present invention, thekneaded material means a general term of the epoxy resin compositioncomponents un-melted in the kneader and the epoxy resin compositionmelted and kneaded in the kneading section.

It is also to be noted that the kneading region 15 means a region fromthe downstream side of a supply orifice 16 in the conveying direction tothe upstream side of the discharge orifice 17 in the conveyingdirection, which is indicated by the arrow in FIG. 1. The kneadingregion, the range in FIG. 1., does not limit a kneading range, and meanscontaining the kneading section 12.

Further, the inner wall 11 a on the downstream side (on the left side inFIG. 1) of the kneading region refers to a semi-cylindrical part of theinner wall 11, which contains the end surface on the downstream side.

As shown in FIG. 1, the biaxial kneader 1 to be used in the presentinvention is mainly comprised of the axial member 10 a for conveying thekneaded material and the axial member 10 b for reversing the kneadedmaterial, the inner wall 11 provided around the axial members 10 a and10 b, the kneading section 12 which is a space formed between the axialmembers 10 a and 10 b and the inner wall 11, and the blower 20 which isa suction means connected to the suction hole 18 provided on thedownstream side of the kneading region in the conveying direction of thekneaded material. Further, the supply orifice 16 and the dischargeorifice 17 are respectively disposed on the upstream side and thedownstream side in the conveying direction of the kneaded material.

The supply orifice 16 of the kneader is provided with a shoot 30 whichserves as a guide for supplying the epoxy resin composition components,and the supply orifice 16 is connected to a bottom end 31 of the shoot30 via screws or the like (not shown). Further, an outside airintroducing pipe 40 is attached to the bottom end 31 of the shoot.

The shape or form of the outside air introducing pipe 40 is notparticularly limited. That is, measures directed toward the preventionof entry of foreign substances, such as setting of a filter (not shown)in the midway between outside air side opening and supply orifice sideopening of the tip end of the outside air introducing pipe 40, orsetting of a filter in the tip end of the outside air introducing pipe40, or bending of the tip end to direct in a downward direction can betaken. The outside air introducing pipe 40 may be attached at a positionshown in FIG. 1, but it may also be attached at any position in thesupply orifice of the kneader or at any position on the upstream side ofthe bottom end 31 of the shoot, as long as it is attached on thedownstream side of an outlet of a resin composition components supplyingmachine.

The discharge orifice 17 is provided with a member for discharge orifice50 in which cooling water is flown for preventing adhesion of thekneaded material.

Further, sheet forming rolls 60 for rolling the kneaded material 65 areprovided in proximity to the discharge orifice 17, if desired.

In the kneader 1, the kneading section 12 is formed by providing theinner wall 11 around the axial members 10 a and 10 b. For the purpose ofdischarging a volatile gas in the kneading section 12 out of thekneader, the blower 20 as a suction means is provided on the downstreamside of the kneading region 15 (shown by the arrow in FIG. 1) of thekneader in the conveying direction of the kneaded material. Preferably,such a blower 20 is provided via the suction hole 18 disposed in the endsurface on the downstream side of the kneader.

With such a structure, it is possible to knead while efficientlydischarging a volatile gas in the kneading section out of the kneaderthrough the suction hole 18 by actuating the suction means. Suchoperation is carried out Simultaneously while introducing outside airinto the kneading section through the supply orifice and the dischargeorifice of the kneader. Outside air is also introduced through thesupply orifice intermittently due to the change of the inside of thekneader.

At this time, it is preferred that the quantity of sucked air out of thekneader is in the range of 3 to 60 m³/h, and outside air is introducedso that the quantity of outside air to be introduced through the supplyorifice (herein below, referred to as the air quantity at the supplyorifice) is in the range of 0.1 to 2 m³/h. More preferably, the quantityof sucked air is in the range of 6 to 30 m³/h, and the air quantity atthe supply orifice is in the range of 0.25 to 1.2 m³/h. If the quantityof sucked air is less than 3 m³/h or the air quantity at the supplyorifice is less than 0.1 m³/h, there is a tendency that the effect ofreducing the quantity of the voids or the frequency of occurrence oftrouble that the kneaded material adheres to the sheet forming rolls islowered. On the other hand, even if the quantity of sucked air exceeds60 m³/h or the air quantity at the supply orifice exceeds 2 m³/h, thereis no difference in effectiveness. Further, sucking of such a largequantity of air is not preferable because there is a possibility thatanother trouble such as clogging of the suction hole 18 due to excessivesuction occurs.

Here, the quantity of sucked air means the quantity of air to be suckedthrough the suction hole 18, and the air quantity at the supply orificemeans the quantity of air to be introduced through the supply orifice16. For example, in FIG. 1, the quantity of sucked air means thequantity of gas to be discharged through the suction hole 18 by blower20, and the air quantity at the supply orifice means the quantity of airto be introduced through a straight part 41 of the outside airintroducing pipe 40 (having a diameter of 50 mm, for example) of thesupply orifice 16.

For example, the quantity of sucked air and the air quantity at thesupply orifice are measured in the following manner. A hole 42 formeasuring the air quantity at the supply orifice is bored in a straightpart 41 of the outside air introducing pipe 40, and an air velocity atthe hole 42 is measured by an anemometer. Then, the measured airvelocity is multiplied by a cross-sectional area of the outside airintroducing pipe 40 to determine the air quantity at the supply orifice.Furthermore, a hole 23 for measuring the quantity of sucked air is boredin a straight part 22 of a suction pipe 21, and an air velocity ismeasured by the above anemometer. Then, the measured air velocity ismultiplied by the cross-sectional area of the suction pipe 21 todetermine the quantity of sucked air.

Outside air is not particularly limited, and an atmosphere in whichoperators can normally work can be employed. Preferably, an atmospherehaving a temperature of 30° C. or lower and a relative humidity of 60%or lower is employed, and more preferably, an atmosphere having atemperature of 20° C. or lower and a relative humidity of 40% or loweris employed. Further, air having a low dew point may be introducedthrough the outside air introducing pipe 40 for the purpose offacilitating volatilization as mush as possible.

In the present invention, by introducing outside air positively into thekneader not only through the discharge orifice 17 but also through theopening of the outside air introducing pipe 40 of supply orifice 16while kneading, the saturation of the volatile gas comes to be reducedand volatilization can be promoted. Therefore, the quantity of avolatile components remaining in the kneaded material is significantlydecreased so that the quantity of a volatile gas to be dischargedthrough the discharge orifice is also decreased. As a result, it ispossible to prevent a phenomenon that a liquid generated by theliquefaction of volatile gas adheres to the sheet forming rolls isprevented. That is, the voids (pores) are hard to be generated whensemiconductor packages are molded. Further, the prevention of adhesionof the above liquid to the sheet forming rolls increases the reliabilityof the kneader.

The kneader to be used in the present invention is not particularlylimited as long as it can knead an epoxy resin composition forsemiconductor encapsulating and can be provided with a suction means.Therefore, a known conventional kneader can be used by providing asuction means. Preferably, a continuous kneader in which an axial memberis covered with a drum body, such as a uniaxial kneader or a biaxialkneader is used in the present invention. In particular, among thesekneaders, a biaxial kneader is preferably used in terms of productionefficiency. Such a kneader is commercially available, and as for anexample of the kneader, “KRC Kneader” manufactured by KURIMOTO, Ltd. canbe mentioned.

The suction means 20 to be used in the present invention is not limitedto any specific one as long as it can discharge a volatile gas in thekneading section out of the kneader. Specifically, a suction means whichhas a capability of sucking a volatile gas in the kneader at 60 m³/h ormore is preferable. For example, a blower or a vacuum pump commerciallyavailable can be used as such a suction means. Among them, a blower(e.g., “HSB Model” manufactured by SHOWA DENKI CO LTD) is preferable asthe suction means since a blower can suck a large quantity of air ascompared with a vacuum suction means such as a vacuum pump.

The above suction means is disposed via the suction hole 18 provided ata predetermined position of the kneader. Here, the suction hole isprovided on the downstream side of the kneading region of the kneader inthe conveying direction of the kneaded material. By providing thesuction hole in such a manner, it is possible to efficiently discharge avolatile gas out of the kneader. Preferably, the suction hole isprovided in an end surface on the downstream side of the kneader asshown in FIG. 1. This is advantageous in that the kneaded material doesnot reach the suction hole.

Another aspect of the present invention is to provide an epoxy resincomposition for semiconductor encapsulating obtained by themanufacturing method according to the present invention. Preferably,there is provided an epoxy resin composition for semiconductorencapsulating containing the inorganic filler in an amount of 70 wt % ormore but 97 wt % or less based on the total weight of the composition.Moreover, the epoxy resin composition for semiconductor encapsulatingobtained by the manufacturing method according to the present inventionis excellent in mold ability, and hence, still another aspect of thepresent invention is to provide a semiconductor device encapsulated withthe epoxy resin composition for semiconductor encapsulating.

Such semiconductor devices of the invention include, for example, resinencapsulating type IC such as DIP (dual inline package), PLCC (plasticleaded chip carrier), QFP (quad flat package), SOP (small outlinepackage), SOJ (small outline J-lead package), TSOP (thin small outlinepackage), TQFP (thin quad flat package) etc., produced by fixing anelement such as semiconductor chip on a lead frame (island tab),connecting a terminal (e.g. a bonding pad) of the element to the lead bywire bonding or bumping, and then encapsulating the semiconductor chipby transfer molding with the epoxy resin composition for semiconductorencapsulating of the invention; TCP (tape carrier package) wherein asemiconductor chip lead-bonded onto a tape carrier was encapsulated withthe epoxy resin composition for semiconductor encapsulating of theinvention; COB (chip on board) wherein a semiconductor chip connected bywire bonding, flip chip bonding or a solder to a wire formed on acircuit board or glass was encapsulated with the epoxy resin compositionfor semiconductor encapsulating of the invention; a semiconductor devicesuch as COG (chip on glass) having a bare chip mounted thereon; hybridIC wherein an active element such as semiconductor chip, transistor,diode, thyristor etc. and/or a passive element such as capacitor,resistance element, coil etc., connected by wire bonding, flip chipbonding, a solder etc. to a wire formed on a circuit board or glass, wasencapsulated with the epoxy resin composition for semiconductorencapsulating of the invention; BGA (ball grid array) produced byinstalling a semiconductor chip on an interposer substrate having aterminal for connection to a multi chip module mother board, thenconnecting the semiconductor chip by bumping or wire bonding to a wireformed on the interposer substrate and then encapsulating thesemiconductor-installed side with the epoxy resin composition forsemiconductor encapsulating of the invention; CSP (chip size package);MCP (multi chip Package) etc.

The most general method of encapsulating a semiconductor device with theepoxy resin composition for encapsulating of the invention islow-pressure transfer molding, but injection molding, compressionmolding etc. can also be mentioned.

EXAMPLES

Herein below, the present invention will be concretely described withreference to examples and a comparative example. It goes without sayingthat the present invention is not limited to the following examples.

Examples 1 to 4 and Comparative Example

(1) Preparation of Epoxy Resin Composition

The following components were mixed:

4.3 parts by weight of a biphenyl type epoxy resin (manufactured byJapan Epoxy Resin Co., Ltd. under the trade name of “YX-4000H”) havingan epoxy equivalent of 196 and a melting point of 106° C.,

0.8 part by weight of a bisphenol A type brominated epoxy resincontaining 48 wt % of bromine and having an epoxy equivalent of 75 and asoftening point of 80° C. (manufactured by Sumitomo Chemical Co., Ltd.under the trade name of “ESB-400T”),

4.8 parts by weight of a phenol novolac resin (manufactured by MeiwaPlastic Industries, Ltd. under the trade name of “H-1”) having asoftening point of 80° C.,

0.2 part by weight of triphenylphosphine,

88 parts by weight of spherical fused silica having an average particlediameter of 17.5 μm and a specific area of 3.8 m²/g,

0.3 part by weight of antimony trioxide,

0.2 part by weight of montanic acid ester (manufactured by ClariantK.K.),

0.2 part by weight of carbon black (manufactured by Mitsubishi ChemicalCorporation under the trade name of “MA-100”), and

0.5 part by weight of γ-glycidoxypropyltrimethoxysilane (epoxysilanecoupling agent).

The mixture was pre-kneaded (dry blending), and was then kneaded using abiaxial kneader in a manner described in the following (2) to obtain anepoxy resin composition for semiconductor encapsulating.

(2) Kneading Test

A kneading test was carried out using the biaxial kneader equipped withsuction means as shown in FIG. 1. In Examples 1 to 4, the mixture waskneaded while carrying out suction, and on the other hand, inComparative Example, the mixture was kneaded without carrying out thesuction. It was observed whether or not a liquid produced byliquefaction of a volatile gas dropped onto sheet forming rolls, andadhesion troubles of the kneaded material to the sheet forming rollswere counted. In addition, there were evaluated voids which weregenerated in molding the kneaded material into packages.

The quantity of sucked air and the air quantity at the supply orificewere measured in the following manner. A hole 42 for measuring the airquantity at the supply orifice was bored in a straight part 41 of anoutside air introducing pipe 40 (diameter: 50 mm) of the supply orifice16, and an air velocity at the hole 42 was measured by an anemometer forvery low velocities (“MODEL ISA-67” manufactured by Sibata ScientificTechnology Ltd.). Then, the measured air velocity was multiplied by across-sectional area of the outside air introducing pipe 40 to determinethe air quantity at the supply orifice. Furthermore, a hole 23 formeasuring the quantity of sucked air was bored in a straight part 22(diameter: 120 mm) of a suction pipe 21, and an air velocity wasmeasured by the above anemometer. Then, the measured air velocity wasmultiplied by the cross-sectional area of the suction pipe 21 todetermine the quantity of sucked air.

The number of occurred troubles was determined as an average value ofthe number of the troubles which occurred during continuously kneading 1ton of the epoxy resin composition for semiconductor encapsulating. Forthe evaluation of the voids, the obtained epoxy resin composition forsemiconductor encapsulating was molded into QFP packages each having asize of 14×20 mm under conditions of 180° C. and 6.9 MPa, and thesurface of each of the molded packages was observed through astereoscopic microscope to determine a ratio of the packages in which apinhole having a diameter of 0.1 mm or more but less than 0.5 mm wasincluded.

Test conditions and test results are shown in Table 1.

TABLE 1 Quantity of Air quantity Presence or sucked air at supplyabsence of (m³/h) orifice (m³/h) liquefaction Example 1 3 0.15 AbsentExample 2 6 0.25 Absent Example 3 30 1.2 Absent Example 4 60 2 AbsentComparative None None Present Example Number of Number of occurredQuantity of clogging of troubles voids suction hole (number/ton) (ppm)(number/ton) Example 1 0.3 2,400 0.0 Example 2 0.2 2,400 0.0 Example 30.03 300 0.0 Example 4 0.02 200 0.01 Comparative 1.1 5,300 — Example

In Examples 1 to 4, it was confirmed that volatile gas in the kneaderdid not liquefy and the quantity of the voids was significantlydecreased. Furthermore, it was also confirmed that the number of theoccurred troubles of the sheet forming rolls were significantlydecreased.

On the other hand, in Comparative Example regarding a conventionaltechnique, it was confirmed that the liquefaction of the volatile gasoccurred and a large amount of the voids was generated. Furthermore, itwas also confirmed that a large number of the troubles of the sheetforming rolls occurred.

As described above, according to the present invention, it is possibleto decrease the quantity of the voids generated in molding thesemiconductor packages, and in addition, the reliability of thesemiconductor device can also be improved. Therefore, the high qualityepoxy resin composition for semiconductor encapsulating can bemanufactured with a high productivity.

(3) Continuous Operation Test

A continuous operation test of the kneader was carried out forconfirming reliability and stability as the kneader to be used in thepresent invention. As a result, it was possible to continuously operatethe kneader used in the present invention for 80 hours or longer underall of the conditions in Examples 1 to 4. Furthermore, the quantity ofthe voids, which were generated in a resin composition obtained bycontinuously operating the kneader for 120 hours under the conditions ofExamples 1 to 4, was evaluated in the same manner as described above. Asa result, good results were obtained similarly to the test results ofExamples 1 to 4.

Therefore, according to the kneader for the epoxy resin composition forsemiconductor encapsulating in the present invention, it was confirmedthat the good epoxy resin composition for semiconductor encapsulatingcan be obtained and in addition the stability of the kneader can beimproved.

As described above, the present invention is not limited to the examplesdescribed above. Therefore, a uniaxial kneader can also be used insteadof the biaxial kneader used in the examples.

INDUSTRIAL APPLICABILITY

In the present invention, since the kneader has a constitution whichenables a volatile gas to be efficiently discharged even underconditions of continuous operation, the quantity of the volatilecomponents remaining in the kneaded epoxy resin composition issignificantly decreased, thereby decreasing the quantity of the volatilegas to be discharged through a discharge orifice. As a result, it ispossible to prevent a phenomenon that a liquid produced by theliquefaction of the volatile gas adheres to the sheet forming rolls.Therefore, the epoxy resin composition for semiconductor encapsulatingwhich enables the quantity of voids to be decreased at the time ofencapsulating a semiconductor device can be manufactured with highproductivity.

1. A method of manufacturing an epoxy resin composition forsemiconductor encapsulating by use of a kneader provided with a suctionhole on the downstream side of a kneading region in a conveyingdirection of the epoxy resin composition, and being provided with asupply orifice and a discharge orifice respectively disposed on theupstream side and the downstream side in the conveying direction of theepoxy resin composition, wherein the kneading region is from thedownstream side of the supply orifice to the upstream side of thedischarge orifice, the method comprising: kneading the epoxy resincomposition, while discharging a volatile gas in the kneader out of thekneader through the suction hole, and simultaneously introducing outsideair to the kneader through the supply orifice and the discharge orifice.2. The method of manufacturing the epoxy resin composition forsemiconductor encapsulating according to claim 1, wherein a quantity ofthe gas to be discharged from the kneader is in the range of 3 to 60m³/h, and the quantity of the outside air to be introduced through thesupply orifice is in the range of 0.1 to 2 m³/h.
 3. The method ofmanufacturing the epoxy resin composition for semiconductorencapsulating according to claim 1, wherein the kneader further includessuction means connected to the suction hole, for discharging thevolatile gas in the kneader out of the kneader through the suction hole,while simultaneously introducing outside air to the kneader through thesupply orifice and the discharge orifice, and wherein in said methodsaid volatile gas is discharged through the suction hole whilesimultaneously introducing outside air through the supply orifice andthe discharge orifice, by operation of the suction means.
 4. The methodof manufacturing the epoxy resin composition for semiconductorencapsulating according to claim 1, wherein the kneader includes a firstaxial member conveying the kneaded material in the kneading region and asecond axial member conveying the kneaded material in a reversedirection to the conveying direction at a downstream side of thedischarge orifice in the conveying direction.
 5. The method ofmanufacturing the epoxy resin composition for semiconductorencapsulating according to claim 1, wherein the kneader includes a wallmember surrounding the kneading region and a region downstream of thekneading region, in the conveying direction, said wall member includingan end wall at an end of said region downstream of the kneading regionin the conveying direction, and the suction hole is provided in the endwall.